Valve stem packing



Jan. 30, N, L MOCHEL VALVE STEM PACKING Filed NOV. 27, 1937 WITNESSES:INVENTOR ZMMX W BY CPI/(517E ATTORNEY NORMHN L. MOCHEL.

Patented s. 30, 1940 Y PATENT oFFicE VALVE STEM PACKING 7 Norman L.Mochel, Ridley Park, Pa., assignor to Westinghouse Electric &Manufacturing Company, East Pittsburgh, Pa., a corporation ofPennsylvania Application November 2'7, 1937, Serial No. 176,908

2 Claims.

My invention relates to a valve for controlling the flow of highpressure, high temperature fluid, particularly to a packing or bushingfor the stem of such a valve, and it has for an object to provide animproved packing.

Another object is to provide a packing or bushing of increasedeifectiveness in preventing the escape of steam around the valve stem.

A further object is to provide a packing or bushing which is both simplein construction and durable.

The bushing of my invention comprises a stack of thin metallic washersof alternately smaller and greater inside diameter, the smaller insidediameter being substantially equal to the diameter of the valve stem,so-that the stem can just slide therethrough but so that leakage offluid is minimized. The intervening washers of greater inside diameterprovide grooves in which foreign matter may lodge. Hence, the danger ofgalling is greatly diminished.

The washers of smaller inside diameter are preferably also of smalleroutside diameter to permit some sliding of these washers, which bear therubbing load.

The above recited and other objects are effected by my invention as willbe apparent from the following description and claims taken inconnection with the accompanying drawing, forming a part thereof, inwhich:

Fig. 1 is a longitudinal sectional view of a high pressure valve showingmy improved packing appliedgthereto;

Fig. 2 is an enlarged sectional view showin my invention more in detail;and

h Fig. 3-is an enlarged plan view of one of the larger elements whichmake up the packing, and having the dimensionsof one of the smallerelements indicated thereon.

Referring now to the drawing in detail, I show my invention embodied ina throttle valve which is adapted, for example, to control the flow ofsteam to a steam turbine, particularly steam at highpressure and hightemperature, for example, 1200 lbs. per square inch and 900 F. Thethrottle valve proper is of usual construction, including a bonnet [0having inlet and outlet openings l l and I2 and a bonnet cover orclosure member l3. The flow of steam through the valve bonnet") iscontrolled by a valve member l4 engaging a seat I5 in the bonnet l0. Itwill be noted that, when the valve is closed, the fiuid pressure abovethe valve exerts a great force holding the valve member againstits seat.In order to partially equalize the. pressures above and below the valvemember Hi to lift the same off 1 its seat, the valve member l4 may beprovided with a port It controlled by a pilot valve ll. The latter is inthe form of a piston movable in a cylinder [8 formed on the valve memberl4. A cover member 99, secured to the valve member I l, forms a closurefor the upper end of the cylinder l8 and is adapted to be engaged by thepiston ll upon upward movement thereof.

The pilot valve I! is rigidly connected to ,a valve stem 2|, which ispreferably made of a 001- rosion-resistant steel, such as stainlesssteel, and

which may be integral with the pilot valve. The upper end of the valvestem 2| slides through a bushing 22 which serves as a guide for thevalve stem.

The valve stem 2! extends through an opening 23 formed in the bonnet l0and is connected to any suitable form of mechanism (not shown) foractuating the valve. The bonnet i0 is formed with a boss or projection24 around the opening 23, and has formed therein a recess 25 in whichpacking 25 is disposed. The packing is retained in the recess byretaining member2l bolted to the boss 2i.

To open the valve, the valve stem 2! is moved upwardly so that the pilotvalve ll opens the port it. Flow through the port I0 eifects a partialequalization of pressure above and below the valve member l4. Uponcontinued upward movement, the pilot valve l'l abuts the cover member l9carried by the valve member M and moves the latter upwardly to effectvalve opening movement of the valve member l4. I

The present invention relates to the packing 20, which comprises, asshown more fully in Figs. 2 and 3, a stack of thin metal plates orwashers 21 and 28 arranged in alternate relation. I prefer to employwashers having a thickness of .010 inch. A different thickness may beemployed, but in order to obtain the full benefits of the presentinvention, it should be not more than inch. While they may be made ofany suitable metal adapted for high pressure, high temperature fluid, Iprefer to make them of stainless or chromium steel containingmolybdenum. The

chromium content provides corrosion resistance.

of 1.010 inch diameter. The washers thus form a series of grooves aboutthe valve stem.

The outer diameter of the washers 28 is substantially equal to thediameter of the recess 25 in the valve bonnet to provide a fluid-tightfit therebetween. The washers 21 are preferably of slightly smallerouter diameter. For example, the outer diameter of the washers 2'! and23 may be 1.740 inch and 1.750 inch, respectively, for the 1 inch valvestem. This permits some sliding of the washers 21, which bear therubbing load. To provide for such sliding, the washers are coated with afilm of graphite, applied in any suitable manner. Some of the excessgraphite Works its way into the grooves and some also works its way inbetween the inner edges of the washers 21 and the surface of the valvestem 2! to provide lubrication thereof.

In Fig. 3, I show one of the washers 28 in plan, and also indicate thedimensions of the washers 21 by dot and dash lines, so that the relativesizes of the washers 21 and 28 may be readily noted therefrom.

The series of grooves formed at the inner edges of the washers servesseveral purposes. Any foreign matter that finds its way between thepacking and the stem is collected in these grooves. In priorconstructions using solid bushings, it has been found that such foreignmatter wedges between the bushing and the stem and frequently causesgalling.

The provision of the large number of small annular grooves in thepacking also provides a labyrinth type of seal, which seal is moreeffective in preventing leakage than a continuous surface.

In this construction, also, the edges of the relatively thin washers 2i,spaced from each other by the larger washers 28, provide a small degreeof flexibility, so that, if foreign particles become wedged in betweensaid edges and the valve stem, said edges may yield.

Another advantage of my new packing is the advantageous relation of thedirectional properties of the metal parts. The fibers of the washersextend at right angles to the surface and the fibers in the valve stem2|, thereby greatly reducing the liability to seizing.

While I have shown my invention in but one form, it will be obvious tothose skilled in the art that it is not so limited but is susceptible ofvarious changes and modifications without de-g parting from the spiritthereof and I desire,

therefore, that only such limitations shall be placed thereupon as areimposed by the prior art or as are specifically set forth in theappended claims. What I claim is: 1. The combination with a having anopening through which said rod extends, of packing for sealing againstleakage of longitudinal movable stainless steel rod or stem and a memberhigh temperature and high pressure fluid through 7 said opening andalong the rod and comprising a stack of thin metallic washers in theopening, each of said washers being of continuous annular formation andformed from chrome molybdenum steel, said stack comprising alternately"arranged first and second washers, the first Washers having openingsconforming closely to the cross section of the stem or rod, and-thesecond washers having openings which are larger than those of the firstWashersand whose boundingedges and the adjacent overlapping portions ofthe first washers provide annular'grooves sepa rated by the latterwashers.

2. Thecombination with a movable stainless steel rod or stem anda-member having asocket through which the, rod or stem extends, of apacking for sealing against leakage of high teme perature and highpressure fiuid through said socket and along the rod or stem andcomprising a stack of thin flexible metallic washers in the socket, eachof said washers being of continuous annular formation and formed fromchrome molybdenum steel, saidstack comprising alternately arranged firstand second washers, the

first washers having openings closely conforming to the stem or rod andthe second Washershaving larger openings whose bounding edgesand theadjacent overlapping portions of the first washers provide annulargrooves separated by the latter washersand the second washers havingtheir peripheries closely fitting the socket walland the first washershaving..,t'heir peripheries] spaced inwardly from such wall in orderthatthey may slide relatively to the second washers.

due to lateral pressures applied thereto by the rod or stem.

NORMAN L. MOCI-LEL.

